This invention relates to riveting apparatus of the type whereby a plurality of tubular rivets may be set in succession by drawing through the bore of each one of the rivets in turn an enlarged head of a riveting mandrel while the rivet is supported by an abutment. Access to only one side of the workpiece is needed, so such rivets are commonly referred to as blind rivets.
Such rivets are well known and widely available under the Registered Trademarks CHOBERT, BRIV and RIVSCREW.
More particularly the invention relates to riveting apparatus of the type in which an elongated mandrel, having an enlarged head at one end and loaded with a plurality of the tubular rivets forming a column of rivets on the mandrel, is gripped by gripping means at or near the end remote from the head, and reciprocated relative to an abutment by relative reciprocation between the gripping means and the abutment, the rivets in the column being fed forwardly along the mandrel so that the leading rivet nearest the mandrel head is positioned between the mandrel head and the abutment and can then be set by moving the mandrel rearwardly relative to the abutment so as to draw the head of the mandrel through the bore of the rivet while the rivet is supported by the abutment. Such apparatus is hereinafter referred to as xe2x80x9criveting apparatus of the type definedxe2x80x9d.
The abutment is usually provided by a nosepiece comprising jaws between which the mandrel extends, and which are separable to allow rivets which are fed forwardly along the mandrel to pass between them, the jaws being spring urged to close together behind a fed rivet which has passed forwardly of the jaws, and to resist rearward movement of the fed rivet. Examples of such riveting apparatus is described in our earlier patent specifications GB 1183049 and GB 2299288, the contents of which are incorporated herein by reference, and to which the reader is referred for an understanding of the field of the present invention.
Such riveting apparatus is well known and much used in the mechanical assembly industry. Examples are widely available under the designations AVDEL 717 Series, AVDEL 727 Series and AVDEL 753 Series (AVDEL is a Registered Trade Mark).
As mentioned, a column of rivets is provided on the mandrel. Typically the column comprises up to about fifty rivets, depending on the length of the rivet. When all of the rivets on the mandrel have been set, use of the apparatus must be temporarily stopped, whilst the mandrel is removed from the apparatus, reloaded with a new column of rivets, and then re-inserted in the apparatus.
Such repeated interruption of the use of the apparatus is very inconvenient under modern production-line conditions, where all stages of the production manufacturing process must be carried out as near continuously as possible with the minimum of interruption.
It is therefore desirable to reduce, as far as possible, the time which it takes an operator to reload a tool. Our previous GB 2299288 describes a number of features which enable the tool reload time to be reduced.
In order to make the rivet setting operation of the tool efficient, one requirement is that, at the start of each rivet-setting stroke of the mandrel, the leading rivet between the mandrel head and the abutment, which is about to be set, has one end in contact with the mandrel head and its other end spaced from the abutment by the minimum distance needed in order to allow the abutment jaws to close behind the rivet after it has been fed through the jaws. This ensures that the minimum initial part of the mandrel stroke is wasted, thereby minimising waste of time and energy. In practical terms, this means that it must be possible to insert the mandrel into the tool in such a way that its head is positioned in the correct relationship to the abutment. Our prior GB 2299288 describes on pages 24 and 25, with reference to FIG. 4D, a means of achieving this by providing a stop at the end of the tool remote from the abutment against which the tail end of the mandrel (i.e. the end remote from the head) abuts, the position of this stop being adjustable in the direction along the mandrel axis. It will be appreciated from the aforementioned description that the construction of that adjustable stop assembly is complicated, and that adjusting it is an awkward operation for the operator.
The tool described in the following example embodiment of the present invention provides a simpler arrangement for adjusting the initial relative positions of the abutment and mandrel head.
Accordingly, the present invention provides, in one of its aspects, riveting apparatus as set out in claim 6.
In the mandrel described in the following example, the tail end of the mandrel is slightly enlarged radially, for example by a crimping operation. However, the means used to feed the column of rivets forwardly along the mandrel is commonly a pneumatic piston with a bore through which the tail end of the mandrel is inserted, as described for example in our prior GB 1183049 and GB 2299288. Since the bore in the piston should be a sufficiently close fit around the mandrel stem that no air (or a minimal quantity of air) escapes between them, initial passage of the tail-end enlargement of the mandrel through the bore of the rivet-feeding pneumatic piston presents a problem. The tool described in the following example incorporates a rivet-feeding device which seeks to overcome this problem.
Accordingly, the present invention provides, in another of its aspects, rivet feeding means as set out in claim 1.